1. Field of the Invention - This invention relates to a method for making a porous carbon article, and more particularly for making an electrode substrate for use in an electrochemical cell such as a fuel cell.
2. Description of the Prior Art - Many methods are known for fabricating porous carbon articles and porous carbon paper, such as might be used as an electrode substrate in an electrochemical cell such as a fuel cell. One method for forming porous carbon paper is described in U.S. Pat. No. 3,829,327. The paper made by the method of that patent is claimed to have good chemical, thermal and structural stability, as well as gas permeability and high electrical conductivity. The method described therein basically involves coating a web of carbon fibers with carbon by a chemical vapor deposition process. The deposition of carbon improves the electrical conductivity of the carbon web, bonds the carbon fibers together, and improves the overall strength of the paper. The process, however, is expensive, in view of the vapor deposition step. Furthermore, at high porosities the paper may not have a strength as high as desirable for certain applications.
Another method for producing a porous carbon sheet is described in U.S. Pat. No. 3,991,169. In that method an alcohol having a boiling point of greater than 150.degree. C. is used as a preliminary binder to form a pitch fiber mat. The mat is then heat treated, including carbonizing in a nonoxidizing atmosphere. During the heat treating the alcohol is burned off while the individual fibers in the mat are fused and bonded to one another at their points of contact.
Two other patents which are representative of the art of making porous carbon sheets are U.S. Pat. Nos. 3,628,984 and 3,960,601. Neither of these methods nor the preceding methods provides the strength, electrical conductivity, porosity, and corrosion protection necessary for certain demanding applications such as for fuel cell electrode substrate applications.